Mass adoption probably won't happen in a way we're expecting it to happen in. I don't think that it will a regular thing to pay for your coffee or dinner using BTC. It may become a way of paying for something online, but I do see it more as a backbone technology and asset of some sort (yet to be determined).
I think the same. Bitcoin (and cryptocurrency in general) has its market niche - eCommerce and remittances, but this niche is much larger than the amount of bitcoins used in it.
The great question affection "bitcoin" itself is what will happen to PoW: if the mining sector can be sustained by growth. If not, there surely will be an advantage for PoS, PoB or PoI coins (PPC, NXT, NEM, SLM etc.).